Refractory waterproof insulating compound.



"rade preferably 950 de ees UNITED STATES PATENT OFFICE.

WILLIAM H. WRIGHT AND JOSEPH HOFFMAN, 0F SCHENECTADY, NEW YORK, ASSIGN- ORS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

No Drawing.

Specification of Letters Patent.

Patented May 3, 1910.

To all whom it may concern:

Be it known that we, WILLIAM H. WRIGHT and JOSEPH HOFFMAN, citizens of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Refractory Waterproof Insulating Compounds, of which the following is a specification.

This invention relates to compounds for insulating electric conductors, protecting portions of.electrical apparatus from heat, i ipporting electrical instruments, and the The object of the invention is to provide for these purposes a cheap and efficient composition of matter which is easily machined, has good insulating properties, is capable of resisting a high degree of heat, and is nonhygroscopic. The composition which we have invented to meet these requirements is made of soapstone and a refractory adulterant, such as clay, ground to a owder and bonded with a flux having a re atively low melting point, such as cryolite. The ingredients are mixed, moistened, molded under pressure, dried and fired.

Entering more into details, it should be stated that the preferred proportions are as follows: soapstone sixty-four parts by weight, clay or other refractory adulterant thirty-four parts, and cryolite four parts, but these figures can be considerably varied to suit requirements. These ingredients are finely ground and mixed together in a moist condition, filled into molds, and subjected to heavy pressure by a hydraulic press or otherwise. The formed article is then removed from the mold, dried, and fired at a temperature of from 900 to 1100 de ees centi- At this cat the 'cryolite fuses slig itly and bonds together the soapstone and clay. It is essential to use a temperature low enough to preserve in an unchanged condition the original properties of the soapstone, so that it will remain in a condition soft enough to be drilled or machined.

In'place of theclay we may use any suitable refractory substance, and as a substitute for the cryolite we ma use any binder having a melting point so lbw that the soapstone Application filed September 4, 1903. Serial No. 172,009.

remains unchanged, such as sodium carbonate, or fluor spar. The cryolite is preferred, however, because it is less hygroscopic than the carbonate and gives a better fluxing effect than fluor spar, the essential point being to use a substance which will satisfac torily bond the soapstone and clay at a low heat and leave the productmoderately hard, tough, and proof against ordinary hygroscopic moisture.

The compound can be used for arc-chutes in controllers, panels for switches, insulators for electric conductors, and in many other places where a fire-proof, non-hy roscopic insulator is wanted. It can be dri led and machined with the same ease as pure soapstone, and its non-hy roscopic qualities make it especially usefu for instrumentsupporting anels in damp locations.

In accor ance with the patent statutes, we have described the principle of operation of our invention together with what We consider to represent the best embodiment thereof; but we desire to have it understood that the invention can be carried out in other ways,-and we do not limit ourselves to the precise ingredients or the exact proportions hereinbefore stat-ed.

What we claim as new and desire to secure by Letters Patent of the United States, is

1. An insulatin compound, consisting of soapstone, a re rectory adulterant, and slightly fused cryolite.

2,. An insulating compound, consistiiu of soapstone, clay and slightly fused cryo lite.

3. An insulating compound, consisting of soapstone, clay and cryolite, ground, moistoned, mixed, compressed and fired sufficiently to sli htly fuse the cryolitea 4. An artificial stoneconsisting of ground soapstone, a refractory adulterant,'and cryo lite fused sufficiently to bind the ingredients together but without destroying the physical characteristics of the soapstone. 1

In witness whereof, we have hereunto set our hands this 3rd day' of September, 1903.-

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

